In an attempt to develop degradable materials such as may be used in biological applications, polymeric matrices have been widely investigated. Degradable matrices have shown potential for many varied uses such as drug delivery agents, scaffolding for tissue growth and development applications, and as in vivo adhesive/barrier agents. High water content materials such as hydrogels formed from cross-linked hydrophilic polymers have been found particularly attractive for both in vivo and ex vivo biological applications. The creation of degradable synthetic hydrogels is particularly desirable for many applications. The use of synthetic materials provides superior control and reproducibility of physical and chemical properties relative to naturally-derived biological polymers, while degradability provides a mechanism for ultimate removal of the material from the body following implantation.
There are numerous methods for hydrogel crosslinking. The creation of degradable synthetic hydrogels has been primarily based on a method developed by Sawheney et al. In this method, hydrophilic polymers containing hydroxyl end groups are used for the ring-opening polymerization of cyclic monomers of alpha hydroxy acids such as glycolide, lactide, and epsilon-caprolactone, resulting in the addition of varying numbers of terminal ester bonds as a function of the degree of polymerization. This method regenerates terminal hydroxyl groups which are subsequently reacted with acryloyl or methacryloyl chloride to generate terminal vinyl groups suitable for free-radical polymerization. While this general method has been widely employed, it is disadvantageous because it requires the use of specialized cyclic monomers that are costly and difficult to obtain in industrial scale quantities, as well as relies upon the use of polymerization reactions which have inherent limitations in controlling the degree of polymerization and reproducibility.
Thus, there is a need for an improved method of making a synthetic degradable hydrogel, particularly a method that may be carried out utilizing common industrial chemical intermediates and alternative reaction schemes. Moreover, there is a need for a synthetic degradable hydrogel that can be readily formed having a controlled, predetermined and consistent degradation rate.